1. Field of the Invention
The present invention relates to a cutter for cutting a continuous corrugated strip. For example, the cutter of the present invention can be used for cutting a corrugated fin used for an automotive radiator or heater into sections having a predetermined length (by a predetermined number of ridges of the corrugated fin).
2. Description of Prior Art
The core of certain types of heat exchangers such as an automotive radiator or heater is manufactured when corrugated fins are welded or soldered to form water tubes. Corrugated fins are obtained when a continuous metallic strip is formed into a wave-shape by a pair of toothed forming rollers or forming gears to form a continuous corrugated strip, which is then sheared by a cutter into sections having a predetermined length (by a predetermined number of ridges of the corrugated fin). For the manufacture of fins on a mass production basis, it is necessary for a cutter to operate at as high speed as possible to shear a corrugated strip discharged continuously at high speed from the forming rollers. Further, the length of corrugated fins varies depending upon the size of the radiator cores to be manufactured. Therefore, it is necessary for the cutter to cut the continuous corrugated strip precisely to obtain a series of strip sections having a desired length.
An example of conventional cutters is disclosed in the specification of U.S. Pat. No. 4,685,318 (or Japanese Unexamined Patent Publication No. 61-159319). This type of apparatus is called a rotary cutter, in which a fixed cutting blade is provided to one of a pair of gears which are opposed to each other and rotated in synchronization with each other, and a movable cutting blade capable of projecting toward the fixed cutting blade is provided to the other gear. When the continuous corrugated fin passing between the opposed gears is cut, the movable cutting blade is projected toward the fixed cutting blade so that the continuous corrugated fin is pinched and cut by the movable and fixed cutting blades like a guillotine.
However, in this type of conventional rotary cutter, the fixed and movable cutting blades are respectively provided to a pair of opposed gears which are synchronously rotated. Therefore, in order to cut the corrugated fin when the two cutting blades collide with each other, that both cutting blades must be shaped and assembled accurately because they are engaged at one point where the outer circles of the opposed gears are in contact with each other. Consequently, it is necessary to use highly accurate parts and assembling techniques, so that the production costs of the conventional apparatus are high.
According to the first conventional technique described above, the cutting blades meet each other at one point on the circumference, at a relative speed of zero, so that the corrugated fin is cut while being pushed by the cutting blades, that is, the first conventional technique is of the push-cutting type. Therefore, the edges of the cutting blades are worn away in a short period of time. The worn edge causes the cutting ability of the blades to deteriorate.
The further problem is that the guillotine type cutter is capable of cutting corrugated fins made of low-ductility materials such as aluminum but is not capable of high-ductility materials such as copper, or thin or wide corrugated fins.
In order to solve the above problems, a cutter is proposed in the specification of U.S. Pat. No. 4,956,987 (or Japanese Unexamined Patent Publication No. 2-36091). A cutter according to a second technique described in these publications utilizes a means which can be called a rotary pinch-cutting type mechanism. As illustrated in FIG. 2, this mechanism includes: several first cutting blades 101 capable of moving in radial slits 108 formed in a feed gear 103; and a second cutting blade 102 capable of moving vertically, wherein the second cutting blade 102 is disposed at a cutting position where the second cutting blade 102 is opposed to the first cutting blade 101. When the first cutting blade 101 is projected onto the outer circumference of the feed gear 103 by the action of a cam 104 in accordance with the rotation of the feed gear 103, the second cutting blade 102 is lowered by the action of another cam 105. In this way, a fin 110 is conveyed between the two cutting blades 101 and 102 while the fin is being cut in its width direction. In this case, the first cutting blades 101 which are not in the cutting position are disposed at retracted positions close to the center of the feed gear 103. Therefore, the first cutting blades 101 do not interfere with guide members 109a, 109b.
However, in the cutter according to the second conventional technique, it is necessary to use a large number of highly accurate parts and dimensions such as: an engaging portion between the first cutting blade 101 and the radial slit 108, an engaging portion between a roller 106 for driving the first cutting blade 101 and a pin 107 for rotatably supporting the first cutting blade 101, an outside diameter of the roller 106, and a height from the center of the pin 107 to the edge of the first cutting blade 101. Therefore, the following problems may be encountered:
The manufacturing costs are increased. It is difficult to increase the operation speed. Problems are caused when chips or debris enter the slits 108. Finally, maintenance of the device is difficult.
Since the cutting machine shown in FIG. 2 is not provided with a mechanism to release an excessive cutting load generated when the upper and lower cutting blades 101, 102 collide with each other, the reliability of the cutting machine is low, and the life of the cutting blades is not long.